The present invention relates to a liquid-permeable topsheet used in disposable fluid absorptive goods such as sanitary napkins and disposable diapers.
Conventionally, disposable body fluid absorptive goods have often employed perforated plastic sheet or nonwoven fabric as material for a liquid-permeable topsheet thereof. In the case of perforated plastic sheet, the sheet is provided with liquid passages extending therethrough from top to bottom thereof and lower openings of the respective liquid passages are arranged in contact with an absorbent core so that excreted body fluids may be transferred rapidly into the absorbent core. Such technique is well known, for example, from Japanese Patent Publication No. 1982-17081 which discloses tapered liquid passages and Japanese patent application Disclosure Gazette No. 1985-259261 discloses cylindrical liquid passages. Use of nonwoven fabric, on the other hand, is preferred to use of a plastic sheet in that the nonwoven fabric offers soft feeling and therefore comfortableness for wearing.
While the conventional technique provides the above-mentioned advantages in its own way, use of the perforated plastic sheet has drawbacks often disliked by the consumer, particularly, slippery feeling and glossy appearance peculiar to the plastic sheet, so there is an acute demand for a topsheet improved to offer feeling as well as appearance similar to cloth as closely as possible. In the case where nonwoven fabric is used as material for the topsheet, the excreted body fluids can be transferred toward the absorbent core as rapidly as when the plastic sheet is used as the topsheet, but the nonwoven fabric falls short of the ability to maintain the top surface of the sheet dry after the body fluids have been transferred toward the absorbent core, i.e., short of a dry touch. In this regard, a proper improvement is demanded. To make the best use of the advantages provided by these conventional materials and compensate for the shortcomings thereof, it has already been proposed, for example, in Japanese patent application Disclosure Gazette No. 1991-51355 to employ a sheet of melt blown nonwoven fabric formed by subjecting thermoplastic fibres to a welding process. While the technique disclosed in this Disclosure Gazette makes it possible to obtain a topsheet having a cloth-like soft feeling as well as a less glossy appearance and provided with liquid passages, the melt blown nonwoven fabric is generally characterized by its relatively small fineness and correspondingly poor elasticity to compression, so the liquid passages are readily collapsed under the body pressure of the user, often with the lower openings of the liquid passages distorted and consequently the body fluids are apt to be prevented from being rapidly transferred toward the absorbent core.
Accordingly, it is an object of the invention to solve the problems as mentioned by constructing a topsheet from an upper sheet layer composed of melt blown nonwoven fibric and provided with liquid passages and a lower fibrous layer underlying the upper sheet layer.